Boom Boxes: 5 Amps That Define the Music We Hear—and the Gear We Play

Marshall 1959 Super Lead

London’s Seventy Six Uxbridge Road must have been an interesting place in 1962: Jim Marshall, a proficient drummer, had just opened a drum shop where he taught future Hendrix drummer Mitch Mitchell, among others. Customers would often bring along their guitar- and bass-playing bandmates, and eventually the shop became a hangout for rockers like Ritchie Blackmore and Pete Townshend.

Conversation often turned to gear, and Marshall—who’d already been making speaker cabinets for bass players—soon learned that the 1957 Fender Bassman that so many players coveted had been discontinued in favor of the 6G6 blonde version. And when he heard that even the coveted ’57 Fenders weren’t giving rockers what they needed, he decided he’d solve the problem with his own design.

It’s worth noting that, though there probably wouldn’t have been any Marshall amps were it not for the untimely demise of the 5F6A Bassman, it’s equally likely the Bassman wouldn’t have existed without the 1951 RCA Receiving Tube Manual’s detailed description of a “High Power Audio Amp.” Each led directly to the other.

In 1962, the Marshall team built their first amp, the JTM45, with the goal of providing guitarists with a more aggressive sound. It wasn’t an exact Bassman clone, just as Leo Fender’s Bassman wasn’t an exact clone of the RCA amp—but in both cases the deviations from the circuit that inspired them were minor. While Marshall followed the Bassman circuit almost identically, they were limited to components available in England.

They first used 5881 (aka 6L6) power tubes, just like the Bassman, but soon changed to KT66s. The JTM45 also used a 12AX7 as the first preamp tube (as opposed to the Bassman’s 12AY7), which resulted in very different gain and loading characteristics. Marshall’s first amp also used an extra brightness capacitor, as well as a feedback circuit taken from the 16-ohm output (rather than the Bassman’s 2-ohm output).

The combination of the JTM45 with Marshall’s 4x12 speaker cabinets hooked the Who’s John Entwistle and Pete Townshend—the latter of whom also contributed design ideas to the Marshall team, which included Dudley Craven and Ken Bran. Alas, by 1965 JTM45 stacks weren’t cutting it for arena acts. The Who switched to 100-watt Vox amps for a time, but purportedly found them unreliable. Townshend then challenged Marshall to double the power of the JTM45.

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Not every version of Marshall’s 100-watt amps was called the 1959 Super Lead. The 1959 name showed up in late 1967, stemming from its item number in a catalog. Regardless, continuing development on the 100-watt head that would eventually be known as the 1959, the company tried four 6V6 power tubes, followed by four 6L6s, then four KT66s.

Four big tubes require a lot of current, and the existing power transformers weren’t up to it. This resulted in a sag-induced compression as the power transformer struggled to keep up. As the team experimented with filter-capacitor values in the power section, they noticed tonal variations. There were also various output-transformer approaches as the quest to refine the circuit continued. Early in 1967, Marshall abandoned KT66s for EL34 power tubes and yet another output transformer. In all, there were no fewer than 15 iterations of the Super Lead between 1965 and 1969—including the mid-’69 switch from Plexiglas to metal control panels.

This rather cursory explanation of the Super Lead’s evolution helps explain vintage-amp junkies’ perennial quest for “a really good plexi.” Compounding the mysteries of the model’s various iterations is the fact that, in those days, electrical component values could vary widely due to less exacting manufacturing methods than are available today. So while any two amps off the line might contain parts labeled with the same values, the cumulative effect of loose component tolerances meant each amp could sound markedly different.

But that didn’t stop the 1959 from going down in history as the 100-watt of choice for everyone from Jimi Hendrix to Eric Clapton, Edward Van Halen, Warren Haynes, Eric Johnson, Yngwie Malmsteen, and many, many others.

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